Preparation And Characterization Of Nanostructured Lipid Carriers Containing Antarctic Krill Oil

Numerous studies have shown that resveratrol and Antarctic krill oil rich in EPA and DHA can effectively protect the cardiovascular and prevent cardiovascular diseases.However,the instability and hydrophobicity of Antarctic krill oil and resveratrol greatly limit their application in water-based foods.As a new-generation carrier system,nanostructured lipid carriers can improve the stability and water solubility of biologically active substances.Therefore,nanostructured lipid carriers containing Antarctic krill oil were developed and their physical and chemical properties were studied to provide theoretical basis and technical guidance for improving the stability of Antarctic krill oil and resveratrol and expanding their application in water-based foods.The main content and results were presented as follows:Firstly,using 1,3-distearic acid glyceride as a solid lipid,a single factor experiment method was used to explore the effect of process parameters(homogenization time,ultrasonic power and time)and formulation factors(emulsifier type and dosage,lipid phase concentration and the ratio of krill oil to total lipid)on the particle size and polydispersity index,and then the methods for preparing Antarctic krill oil NLC were optimized.It was found that homogenization time,ultrasonic power and time,emulsifier type and concentration,total lipid phase concentration and the proportion of krill oil in the lipid phase all affect the particle size and PDI of NLC.The optimized NLC dispersion,formulated by 2%(w/w)lecithin and 10% total lipid of which krill oil accounted for 50%(w/w)and mixed by a high-speed dispersion homogenizer at 25000 r/min for 2 min,was prepared after 8 min ultrasonication at 380 W.The particle size and PDI of the optimized NLC was 112.4 ± 0.4 nm,0.270 ± 0.004 respectively,indicating good dispersion uniformity and stability.Secondly,8 different solid lipids were selected to prepare NLC containing Antarctic krill oil.Particle size,PDI,morphology,thermodynamic and crystalline characteristics,retention rate of EPA were studied to investigate the inherent relationship between solid lipid material and NLC.It was found that the three types of fatty acids with different carbon chain lengths are not suitable for the preparation of NLC.Although glyceryl monostearate,glyceryl 1,3-distearate and glyceryl tristearate had the same carbon chain length,only glyceryl 1,3-distearate and glyceryl tristearate can be used in the successful development of Antarctic krill oil NLC.Three kinds of solid triglycerides with different carbon chain lengths can be used to prepare Antarctic krill oil NLC that meets the scale requirements and have good uniformity and stability.As the carbon chain on the glycerol skeleton changed from C12 to C18,the particle size of NLC increased from 235.80 ± 2.30 nm to 340.50 ± 2.20 nm,and the retention rate of EPA dropped from 88.72±0.47% to 72.86±1.06%.In addition,there was a high degree of correlation between the carbon chain length and particle size,retention rate.The particle size is also highly correlated with the EPA retention rate.When it comes to 4 kinds of Antarctic krill oil NLC successfully prepared,their PDI were all below 0.30 and zeta potential also exceeded-30.00 m V,showing that NLC with a single dispersion and good physical stability were successfully produced.Transmission electron microscopy(TEM)revealed that the NLC particles were spherical or oval,indicating that the type of solid lipid had no significant effect on the NLC morphology.The results of XRD and DSC showed that the NLCs prepared from 4 different solid lipid all have disordered defect crystals.Thirdly,the physical stability,oxidation stability and freeze-drying stability of GDS-NLC prepared from glyceryl 1,3-distearate were evaluated.The results were as follows: The GDSNLC centrifugal stability parameter was only 1.07%,showing that GDS-NLC had excellent centrifugal stability.After storing at 4 °C,20 °C,and 40 °C for 15 days,the average particle size of GDS-NLC still remained within the scope of 110-120 nm,though increased by 4.77%,4.66%,and 5.49%,respectively.And PDI were also still below 0.3.It showed that GDS-NLC has good storage stability.By comparing the POV value of Antarctic krill oil and GDS-NLC stored at different temperature for 15 days,it was found that the POV value of GDS-NLC and krill oil changed slowly with storage time at 4 °C and 20 °C.At 4 °C,the POV value of NLC is the lowest,which is most conducive to the preservation of NLC.Under the storage condition of 40 °C,although the POV value of GDS-NLC during 0-5 d was higher than krill oil,the POV value of GDS-NLC between 5-15 d was lower than krill oil.With the extension of storage time,NLC can effectively protect krill oil,and the oxidation process of GDS-NLC at 40 °C conformed to the first-order oxidation kinetics.By detecting the volatile substances of GDSNLC stored at 40 °C,no typical Strecker degradation products were found.It was speculated that no non-enzymatic browning reaction of Strecker degradation form occurred in GDS-NLC.The freeze-drying experiment found that different kinds of cryoprotectants could improve the freeze-drying stability of GDS-NLC,and 2% sucrose had the best protection effect on GDSNLC.After reconstitution,the particle size was 162.4 ± 1.3 nm,and the PDI was 0.228 ± 0.003,indicating that it still maintained good stability,which laid a theoretical foundation for the application of GDS-NLC in milk powder and other solid powder products.Finally,R-NLC loaded with resveratrol was prepared based on GDS-NLC.By comparison,it was found that the average particle size,PDI and Zeta potential between R-NLC and GDSNLC were not significantly different,indicating that the introduction of resveratrol had no significant effect on the physical stability of GDS-NLC.The encapsulation efficiency of resveratrol in R-NLC was as high as 97.76±0.01%,showing that GDS-NLC has the feasibility of encapsulating resveratrol.Besides,the DPPH free radical scavenging rate of R-NLC was higher than that of resveratrol ethanol solution,elucidating that GDS-NLC can effectively protect resveratrol from oxidation.In addition,R-NLC can play a role in slowing down the release of resveratrol.Probably,a combination between erosion and diffusion contributed to the release of the resveratrol from the lipid matrix of the nanoparticle,and its release rule was more in line with the Ritger-Peppas equation.